A virtual array of loudspeakers surrounding a listener is commonly used in the creation of a virtual spatial acoustic environment for headphone delivered audio. The sound field created by this speaker array can be manipulated to deliver the effect of sound sources moving relative to the user or in order to stabilize the source at fixed spatial location when the user moves their head. These are operations that are of major importance to the delivery of audio through headphones in Virtual Reality (VR) systems.
The multi-channel audio, which is processed for delivery to the virtual loudspeakers, is combined to provide a pair of signals to the left and right headphone speakers. This process of combination of multi-channel audio is known as binaural rendering. The commonly accepted most effective way of implementing this rendering is to use a multi-channel filtering system that implements Head Related Transfer Functions (HRTFs). In a system based on a number, for example, M, (where M is an arbitrary number) of virtual loudspeakers, the binaural renderer will need to have 2M HRTF filter as a pair is used per loudspeaker to model the transfer function between the loudspeaker and the user's left and right ears.